Synergistic strengthening through moderate B2 phase and smallest grain size for enhanced wear resistance in Ti2Zr0.75NbVAlx lightweight refractory high-entropy alloys

Abstract

In this study, we systematically investigate the synergistic effect of B2 phase content and grain size on the friction and wear performance of Ti₂Zr_0.75NbVAl_x (x = 0.1, 0.3, 0.5, 0.7, 0.9) lightweight refractory high-entropy alloys (LRHEAs). Microstructural characterization reveals that the Al0.7 alloy exhibits a moderate B2 phase fraction and the smallest grain size (236.82 μm), leading to superior wear resistance compared to alloys with either minor or excessive B2 phase content (Al0.7 alloy wear rate: 3.6358 × 10⁻⁴ mm³/N·m). Molecular dynamics (MD) simulations demonstrate that the combination of a moderate B2 phase and fine grained structure effectively suppresses dislocation multiplication and propagation during friction, minimizing surface damage. The enhanced performance of the Al0.7 alloy is attributed to the synergistic strengthening mechanism: the ordered B2 phase impedes dislocation multiplication, while high-density grain boundaries further restrict dislocation mobility. These findings provide critical insights into the design of advanced wear-resistant LRHEAs by optimizing phase composition and grain refinement, offering a promising pathway for developing high-performance structural materials.